1. Field of the Invention
The present invention relates to a substrate transfer apparatus for transferring a substrate between modules, a substrate transfer method, and a non-transitory storage medium storing a program for executing the substrate transfer method.
2. Description of the Related Art
In a manufacturing process of, for example, a semiconductor device, a plurality of treatment modules each performing treatment on a wafer being a substrate are provided in an apparatus and the wafer is sequentially transferred by a substrate transfer apparatus between the treatment modules, whereby predetermined treatments are performed. The substrate transfer apparatus includes a holding part holding the wafer.
For performing appropriate treatments on the wafer, it is required to accurately deliver the wafer to a predetermined position in the module. To this end, it is studied to detect the position of the edge portion of the wafer on the holding part by a detection part (sensor) and transfer the wafer on the basis of the detected position. For example, in Japanese Laid-open Patent Publication No. H08-031905, it is described to correct the transfer amount of the wafer between the modules on the basis of the detected position of the edge portion of the wafer so as to eliminate the positional displacement of the wafer in the module. It is also described in Japanese Laid-open. Patent Publication No. 2006-351884 to obtain a center position of the wafer from the detected positions of the edge portion and to conduct control for a transfer arm part to be able to move and mount the wafer to a transfer target position on the basis of the displacement amount between the center position and a predetermined reference position.
However, the wafer is not a round but has a cutout (notch) for positioning of the wafer formed at its edge portion. When a detection range of the detection part overlaps with the cutout, the position of the wafer at the holding part cannot be correctly detected any longer, and therefore, something needs to be done. Further, in the case of failure of the plurality of detection parts due to some problem, it is conceivable that the transfer of the wafer under treatment in the apparatus is stopped and an operator enters the apparatus to collect the wafer and removes the wafer. In this case, however, the treatment on the wafer is suspended in the apparatus and the throughput may greatly decrease. In such circumstances, it is desired to accurately detect the position of the wafer even when a part of the plurality of detection parts are unusable. The apparatuses in Japanese Laid-open Patent Publication No. H08-031905 and No. 2006-351884 in which these problems are not into consideration cannot solve the problems.